The present invention relates to loudspeaker enclosures of the low frequency exponential folded horn type intended for corner placement. In particular, the present invention features a unitary horn pathway and exhausts upward into the trihedron formed by two walls and a ceiling, and uses the right-angle vertical walls as the terminal section channel boundaries of the horn, producing an effective extension of the horn expansion beyond the confines of the physical enclosure.
There are several prior art examples of low frequency folded corner horn enclosures which use the planar surfaces of walls and either the conjoined floor or ceiling to complete the horn pathway. For example, U.S. Pat. No. 2,373,692 to Klipsch and U.S. Pat. No. 2,815,086 to Hartsfield, both of which teach a bifurcation of the horn pathway which in turn exhausts on both outer sides of a central planar baffle, relying on the proximity of the corner walls to maintain a waveform boundary until at such distance traveled, the appropriate mouth size is achieved beyond the limits of the physical enclosure. Exhausting the horn horizontally along the sidewalls of a corner imposes the requirement of having no obstructions along both corner walls and floor at least in the distances required in order to achieve an appropriate mouth size and propagate the low frequency waveform with the least distortion. The imposed requirements on the listening space can be seen to increase the effective footprint size of the prior art horn devices mentioned previously.
The U.S. Pat. No. 2,754,926 to Rice teaches the benefits of exhausting upwards into the corner from a back-loaded horn device. The Rice invention exhausts the terminal horn section vertically using the dihedral walls as external channel boundaries after the waveform leaves the physical confines of the enclosure exit channels.
It can be seen that the most important benefit of an upward exhausting corner horn is that the requirement for side walls proximate to the corner to be free of obstructions is entirely removed, and that a device using the principle of exhausting from the top makes no further requirements on the listening space other than having corners for proper placement and the actual footprint of the device on the available floor space.
In the Home Theatre (HT) marketplace, especially, it may be specifically desirable to have obstructions along both the side walls and front wall of a dedicated listening space, such as large screen televisions, equipment cabinetry, furniture, and the like. The HT market is also most likely to find large enclosures appealing for the sonic performance they tend to produce, further enhanced by the likelihood that ample floor space may be available for them in a dedicated HT environment. In such a space, the probable position for front mains speakers would likely be in the front corners.
The formulas for calculating the values of exponential horns are well known in the art. Such examples can be found in the text “How to Build Speaker Enclosures”, by Alexis Badmaieff and Don Davis, Howard W. Sams and Company, Indianapolis, Ind., 13th printing (1978) pages 86 through 91. The formulas regarding the interrelationship of horn and driver are defined by D. B. Keele, Jr., “Low Frequency Horn Design Using Theile/Small Driver Parameters”, AES Preprint #1250, 1977.
The use of multiple flare rates are described by H. Olson in “Acoustic Engineering”, D. Van Nostrand, Inc., 1957, and Klipsch and Delgado, “A Revised Low-Frequency Horn of Small Dimensions”, AES Vol. 48, No. 10, October 2000. Optimum mouth size is calculated using D. B. Keele, Jr., “Optimum Horn Mouth Size”, AES Preprint No. 933, September, 1973.
A loudspeaker enclosure capable of reproducing the low frequency dynamic range available with current digital technology, with low distortion, employing a relatively small corner footprint, and which does not make many demands on decor or on room proportions would seem to be highly desirable.